The present invention relates to a communication systems. More particularly, the invention pertains to a multi-mode communications system.
Recently, there has been increased research and development with respect to Radio Frequency Identification (xe2x80x9cRFIDxe2x80x9d) device tags. These RFID tags essentially comprise small radio transceivers attached to a movable object. By coupling an RFID tag to an object, it has been intent of developers of creating a system for tracking the whereabouts and identification of the object.
Several RFID systems have been developed. Generally, these designs have been relatively large in sizexe2x80x94approximately cigarette packagexe2x80x94and have been generally fabricated using hybrid circuit techniques. Besides their bulky size, the systems require the RFID tag to constantly remain activated.
Recently, there have been several breakthroughs in techniques in the design and manufacture of RFID tags. Examples of these include xe2x80x9cRadio Frequency Identification Device (RFID) and Method of Manufacture, Including an Electrical Operating System and Method,xe2x80x9d U.S. patent application Ser. No. 899,777, filed on Jun. 17, 1992, xe2x80x9cAnti-Theft Method for Detecting The Unauthorized Opening of Containers and Baggage,xe2x80x9d U.S. patent application Ser. No. 921,037, Jul. 24, 1992, xe2x80x9cElectrically Powered Postage Stamp or Mailing or Shipping Label Operative with Radio Frequency (RF) Communications,xe2x80x9d U.S. patent application Ser. No. 928,899, filed on Aug. 12, 1992, and xe2x80x9cModulated Spread Spectrum in RF Identification Systems Method,xe2x80x9d U.S. patent application Ser. No. 032,384, filed on Mar. 17, 1993, all commonly assigned to Micron Semiconductor, Incorporated, and all incorporated herein by reference.
It has been thus a design criteria that these RFID tags be light weight and inexpensive. However, these systems previously have not addressed the need of low power consumption. Presently, RFID tags must be active to detect their location, as well as additional information. As such, there is a need to develop a RFID tag communications system having an active mode for receiving/transmitting data and a sleep mode for reducing power consumption.
In order to achieve the benefits of the present invention, a system is disclosed comprising a first communications device for receiving data and a wake up signal. The first communications device comprises an active mode of operation and a sleep mode of operation for reducing power consumption. Further, the system comprises means for switching the first communications device to and from sleep mode in response to receiving the wake up signal. Further, the system comprises a second communications device for transmitting data to the first device during its active mode, while transmitting the wake up signal to the first device during its sleep mode.
Moreover, a method is disclosed for reducing the consumption of energy in operating a communications system. The communications system comprises a transmitter, a master receiver and a wake up receiver. The master receiver has at least an active mode and a sleep mode of operation and the wake up receiver using substantially less power than the master receiver. Initially, data is transmitted to and received by the master receiver during its active mode, while a wake up signal is transmitted and received by the wake up receiver during the master receiver""s sleep mode. It should be noted that the wake up signal comprises a predetermined frequency and a predetermined rate of data transmission. Subsequently, the predetermined frequency and a predetermined rate of data transmission signal are detected. Upon detecting both, the master receiver is enabled for receiving data system in response to detecting the wake up signal.
The objects and advantages of the present invention will become apparent to those skilled in the art from the following detailed description read in conjunction with the appended claims and the drawings attached hereto.